Expandable intervertebral cage assemblies

ABSTRACT

An expandable assembly for insertion into an intervertebral space is presented. The assembly, in particular aspects, includes an elongate body comprising an upper portion and a lower portion, wherein the elongate body defines an internal longitudinal channel extending from a proximal opening to a distal cavity. The assembly may include an expander that is sized and shaped for insertion into the distal cavity, thereby selectively expanding the upper portion away from the lower portion. The elongate body may also include one or more bone graft windows a cap that is sized and shaped for insertion into the proximal opening.

CONTINUITY

This application claims the benefit of, priority to, and is acontinuation-in-part of U.S. application Ser. No. 13/962,879, titledEXPANDABLE INTERVERTEBRAL CAGE ASSEMBLIES AND METHODS, filed on Aug. 8,2013, which claims priority to and the benefit of U.S. Application No.61/680,729, titled EXPANDABLE INTERVERTEBRAL CAGE ASSEMBLIES ANDMETHODS, filed on Aug. 8, 2012; and U.S. Application No. 61/787,744,titled EXPANDABLE INTERVERTEBRAL CAGE ASSEMBLIES AND METHODS, filed onMar. 15, 2013; all of which are incorporated herein in their entirety.

BACKGROUND

The following disclosure relates generally to medical devices, systemsand methods, including, for example, systems and methods for lumbarinterbody fusion.

Surgical implantation of disc replacement material is typically used toprovide support along the spinal column in cases where a portion of thepatient's intervertebral anatomy has become weakened, diseased, ordestroyed. Such support systems are also commonly used following adiscectomy, where an intervertebral disc is surgically removed.

Most commonly, existing support systems typically operate by inhibitingnormal movement between the adjacent vertebrae, thereby holding thesevertebrae at fixed positions relative to one another, with themechanical body of the supporting structure providing the needed supportalong the patient's spinal column. Such supporting systems are typicallymade of stainless steel, titanium, polymer (e.g., an organic polymerthermoplastic such as polyether ether ketone (PEEK)), carbon fiber, orceramic and they are designed to permanently remain within the patient'sbody.

It is beneficial, in addition to fixation, to try to stimulate bonegrowth between the adjacent vertebrae. To do so, spine surgeons use bonegraft material in addition to fixation devices. Bone graft doesn't healor fuse the spine immediately; instead, bone graft provides a foundationor scaffold for the patient's body to grow new bone. Bone graft canstimulate new bone production. When new bone grows and solidifies,fusion occurs. Although instrumentation (e.g., screws, rods) is oftenused for initial stabilization (post-operative), it is the healing ofbone that welds vertebrae together to create long-term stability. Thereare two general types of bone grafts: real bone and bone graftsubstitutes. Real bone can come from the patient (autograft) or from adonor bone (allograft). Also used in these types of surgery are bonesubstitute, osteoinductive agent, and bone cement.

There is a need for improved systems and methods for lumbar interbodyfusion.

SUMMARY

An expandable assembly for insertion into an intervertebral space isdisclosed. The assembly, in particular aspects, includes an elongatebody comprising an upper portion and a lower portion, wherein theelongate body defines an internal longitudinal channel extending from aproximal opening to a distal cavity. The assembly may include anexpander that is sized and shaped for insertion into the distal cavity,thereby selectively expanding the upper portion away from the lowerportion. The elongate body may also include one or more bone graftwindows a cap that is sized and shaped for insertion into the proximalopening.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the preferred embodiments of the presentinvention will become more apparent in the detailed description in whichreference is made to the appended drawings wherein:

FIG. 1A is a perspective view of one aspect of an expandable cage forinsertion into an intervertebral space in an unexpanded position;

FIG. 1B is a perspective view of the expandable cage of FIG. 1A in anexpanded position;

FIG. 2A is a side elevational view of the expandable cage of FIG. 1A inthe unexpanded position;

FIG. 2B is a side elevational view of the expandable cage of FIG. 1A inthe expanded position;

FIG. 3A is a proximal end elevational view of the expandable cage ofFIG. 1A in the unexpanded position;

FIG. 3B is a proximal end elevational view of the expandable cage ofFIG. 1A in the expanded position;

FIG. 4A is a side elevational cut away view of the expandable cage ofFIG. 1A in the unexpanded position, cut along line 4A-4A in FIG. 3A;

FIG. 4B is a side elevational cut away view of the expandable cage ofFIG. 1A in the expanded position, cut along line 4B-4B in FIG. 3B;

FIG. 5A is a top plan view of the expandable cage of FIG. 1A in theunexpanded position;

FIG. 5B is a top plan view of the expandable cage of FIG. 1A in theexpanded position;

FIG. 6A is a side elevational view of an expandable cage in anunexpanded position associated with an insertion tool;

FIG. 6B is a side elevational view of an expandable cage in an expandedposition associated with an insertion tool;

FIG. 7 is a perspective view of an expander for use in an expandablecage;

FIG. 8A is a perspective view of one aspect of an expandable cage in theunexpanded position;

FIG. 8B is a perspective view of the expandable cage of FIG. 8A in theexpanded position, showing at least one tongue in the distal end of theupper and lower portions for complimentary fit into a recess definedtherein the expander;

FIG. 9A is a partially transparent perspective view of FIG. 8A;

FIG. 9B is a partially transparent perspective view of FIG. 8B;

FIG. 10 is a perspective view of the expander of FIGS. 8A and 8B;

FIG. 11 is a perspective view of the upper portion of FIGS. 8A and 8B;

FIG. 12 is a perspective view of the lower portion of FIGS. 8A and 8B;

FIG. 13A is a perspective view of one aspect of an expandable cage inthe expandable position, showing at least one hook positioned on theinner surface of the upper and lower portions configured forcomplimentary receipt into a recess defined in the distal portion of theexpander;

FIG. 13B is a perspective view of the expandable cage of FIG. 13A in theunexpanded position;

FIG. 14 is a partially transparent perspective view of one aspect of anexpandable cage for insertion into an intervertebral space in anexpanded position;

FIG. 15 is a cut-away perspective view of the expandable cage of FIG.14, cut along line 15-15 in FIG. 14;

FIG. 16 is a perspective view of an actuating screw of the expandablecage of FIG. 14;

FIG. 17 is a cut-away perspective view of the actuating screw of FIG.18, cut along line 16-16;

FIG. 18 is a perspective view of an insertion tool;

FIG. 19 is a perspective view of a medical device system having anexpandable cage and an insertion tool:

FIG. 20 is a perspective view of the outer sleeve of the insertion toolof FIG. 18; and

FIG. 21 is a perspective you of the drive rod of the insertion tool ofFIG. 18.

DETAILED DESCRIPTION

The present systems and apparatuses and methods are understood morereadily by reference to the following detailed description, examples,drawing, and claims, and their previous and following description.However, before the present devices, systems, and/or methods aredisclosed and described, it is to be understood that this invention isnot limited to the specific devices, systems, and/or methods disclosedunless otherwise specified, as such can, of course, vary. It is also tobe understood that the terminology used herein is for the purpose ofdescribing particular aspects only and is not intended to be limiting.

The following description of the invention is provided as an enablingteaching of the invention. To this end, those skilled in the relevantart will recognize and appreciate that many changes can be made to thevarious aspects of the invention described herein, while still obtainingthe beneficial results of the present invention. It will also beapparent that some of the desired benefits of the present invention canbe obtained by selecting some of the features of the present inventionwithout utilizing other features. Accordingly, those who work in the artwill recognize that many modifications and adaptations to the presentinvention are possible and can even be desirable in certaincircumstances and are a part of the present invention. Thus, thefollowing description is provided as illustrative of the principles ofthe present invention and not in limitation thereof.

As used throughout, the singular forms “a,” “an” and “the” includeplural referents unless the context clearly dictates otherwise. Thus,for example, reference to “a” component can include two or more suchcomponents unless the context indicates otherwise. Also, the words“proximal” and “distal” are used to describe items or portions of itemsthat are situated closer to and away from, respectively, a user oroperator such as a surgeon. Thus, for example, the tip or free end of adevice may be referred to as the distal end, whereas the generallyopposing end or handle may be referred to as the proximal end.

Ranges can be expressed herein as from “about” one particular value,and/or to “about” another particular value. When such a range isexpressed, another aspect includes from the one particular value and/orto the other particular value. Similarly, when values are expressed asapproximations, by use of the antecedent “about,” it will be understoodthat the particular value forms another aspect. It will be furtherunderstood that the endpoints of each of the ranges are significant bothin relation to the other endpoint, and independently of the otherendpoint.

As used herein, the terms “optional” or “optionally” mean that thesubsequently described event or circumstance may or may not occur, andthat the description includes instances where said event or circumstanceoccurs and instances where it does not.

Presented herein are systems, tools, and methods for supporting adjacentvertebrae of the spine, for example, as part of interbody spinal fusionsurgery. Although the systems, tools, and methods are presented hereinin the context of posterior lumbar interbody fusion (PLIF), directlateral interbody fusion (DLIF), and transforaminal lumbar interbodyfusion (TLIF), the assemblies and techniques may be useful in a varietyof therapeutic contexts.

In one aspect, a cage assembly for the stabilization of anintervertebral space during a spinal fusion procedure is presented. Asdescribed herein, the cage assembly may comprise an expander such as anexpansion screw or a shim which, when inserted, selectively expands thebody of the cage assembly to a desired size. The cage assembly mayinclude one or more openings or windows for receiving bone fusionmaterial. The bone fusion material may comprise, for example and withoutlimitation, autologous bone, allograft bone, bone substitute,osteoinductive agent, and/or bone cement. The cage assembly may alsoinclude a plug or cap to contain the bone fusion material and to addstrength to the trailing side of the cage in weight bearing.

In one aspect, a cage assembly 1000 may include a generally elongatecage body 1010, an expander 1032, and an insertion tool 1060, as shownin FIG. 1A.

The cage body 1010 may be generally rectangular in cross-section. Thebody 1010 may include an upper portion 1012 and a lower portion 1018.The outer surfaces of the two portions 1012, 1018 may be ridged orgrooved, laterally, as shown. The two portions 1012, 1018 may be joinedtogether by a pin-in-slot joint or another type of hinge 1070 near theproximal end. The space between the two portions 1012, 1018 may form aninternal space, cavity, or channel 1020 that extends lengthwise throughthe cage body 1010. The cage body 1010 may also include one or moreopenings or windows 1050 for receiving bone fusion material.

As illustrated in FIG. 1A and FIG. 1B, the expander 1032 may be a keyedshim. Referring to the perspective view in FIG. 1A, the shim has “key”on its distal portion. In this particular aspect, the key is generallyconical in cross-section with a rectangular or square end, like the headof a bolt, and tapered on both sides. The key shape on the distalportion may be sized and shaped to fit within a distal cavity 1030, asshown in Section A-A. In one aspect, the expander 1032 may include a setof keyed shims, each key having a discrete size and shape. The cage body1010 may also include a number of cage bodies, each with a distal cavity1030 having a different size and shape. The size and shape of the key,together with its matching distal cavity 1030, may be used to create acage body 1010 that opens to a desired height and angular orientation.

Referring again to the perspective view in FIG. 1A, the proximal end ofthe keyed shim may include a proximal portion 1078, which can be seenthrough the window 1050 in the upper portion 1012. The proximal portion1078 of the shim may include a socket or other feature for receiving thedistal end of an insertion tool 1060. The tool may be used to pull thekeyed shim 1032 proximally until the key slides into the distal cavity.One aspect of a keyed shim 1032 is also illustrated in FIG. 2. As shown,the proximal portion 1078 may be generally cylindrical in shape and maybe suitable for grasping by the distal end of an insertion tool. Thekeyed shim 1032, as shown, may also include side rails that are sizedand shaped to engage with interior portions of the cage body 1010.

The insertion tool 1060, as shown in FIG. 1B, may include a cannula 1062and a drive rod 1068. The distal end of the drive rod 1068 may include aspecialized head or other tool for grasping or otherwise engaging theproximal portion 1078 of the keyed shim; e.g., a threaded portion. Onceengaged, the drive rod 1068 may be used to pull the keyed shimproximally, or push it distally, into a desired position. Alternatively,the threaded rod may be rotated in order to actuate a change in theposition of the expander 1032 to the desired position.

As shown in FIG. 1B, the expander 1032 or keyed shim, when pulledproximally and into the distal cavity 1030, will cause the two portions1012, 1018 of the cage body 1010 to expand or spread open. Thepin-in-slot joint or hinge 1070 may allow the two portions 1012, 1018 toexpand or move vertically relative to one another, while also allowingthe two portions 1012, 1018 to rotate about the hinge 1070 therebychanging the angle of the upper portion 1012 and the lower portion 1018of the body. In this aspect, the keyed shim 1032 may induce an angularrelationship in which the distal end of the cage body 1010 becomes moreopen than the proximal end. The cage body 1010, as shown, may alsoinclude a set screw 1042 for insertion into the proximal portion 1078 ofthe keyed shim. The drive rod 1068 or another tool inserted through thecannula 1062 may be used to rotate or otherwise drive the set screw 1042into position. The set screw 1042, in one aspect, may be sized andshaped to retain the expander 1032 firmly within its final position,such that the expander 1032 will not retreat or otherwise “back out”unless purposely driven by a tool, also aiding in containment of thefusion material within the cage assembly and strengthening the proximalwall of the construct.

In use, the cage assembly 1000 may be inserted using an insertion tool1060 into an intervertebral space; for example, in the lumbar region ofthe spine. A drive rod 1068 or other tool may be used to grasp orotherwise engage with a proximal portion 1078 of the expander 1032, andpull the expander 1032 proximally until its distal “key” is seatedwithin a distal cavity 1030. Section B-B of FIG. 1B shows the key of theexpander 1042 seated within the distal cavity 1030.

In certain exemplified aspects, the cage assembly 1000 comprises meansto prevent the separation of the upper portion 1012 and the lowerportion 1018 prior to expansion. In one aspect, the distal portion 1080of the shim 1032 defines at least one substantially longitudinal slot,groove, or recess 1082. As shown in the figures, the distal portion ofthe shim can define a slot, groove, or recess on either side surface1084. In this aspect, the distal end 1113 of the upper portion 1012 andthe distal end 1119 of the lower portion 1018 each comprise a tongue1120, 1122 sized such that both tongues can slide into and be retainedwithin one of the recesses 1082 defined in the distal portion of theshim. The upper and lower portion can also have bilateral tongues, asshown in the figures. Referring to FIGS. 5 and 6, in the unexpandedposition, the tongues from both the upper and lower portion are retainedwithin the recess(es) by portions of the shim. This permits insertion ofthe cage without the potential of the premature separation of the upperand lower portions. As the shim is moved proximately, the recess ismoved proximately, while the tongues remain unmoved, essentiallydisengaging the tongues and recesses. Once the shim is movedsufficiently, the tongues disengage from the recess, enabling the upperand lower portions to expand as designed.

In another exemplified aspect, as illustrated in FIGS. 10 and 11, theupper and lower portions can comprise a tongue, pin, or hook 1120, 1122positioned on each of their inner surfaces 1114, 1117. In this aspect,the distal portion of the shim defines a recess, slot, or hollowcorresponding to each tongue, pin or hook such that, when the cage is inthe unexpanded position, the hooks of the upper and lower portions areretained within the slots in the distal portion of the shim. As the shimis moved proximately, the slots are also moved proximately, while thehooks remain unmoved, essentially disengaging the hooks and slots andpermitting expansion of the upper and lower portions.

In still another aspect, the upper and lower portions may be bondedtogether in a temporary fashion so they do not splay during insertion.For instance, a portion of the lower portion may be ultrasonicallywelded, glued, or otherwise bonded to a portion of the upper portion.Then, after insertion, the bond can be broken during and by theexpansion of the upper and lower portions. It is also contemplated thatthe bond can be between the upper and/or lower portion and the insert.

Bone fusion material may be inserted into the one or more windows 1050into the cage body 1010 as well as through the aperture 1040 in theproximal end of the expander 1078, and thereby into the proximity of thesurrounding bony structures, in order to promote fusion and to furthersecure the cage assembly 1000 in place.

Either before or after placement of the bone fusion material, a cap orset screw 1042 may be inserted (using a drive rod 1068 or another toolinserted through the cannula 1062) into the proximal portion 1078 of theshim. The set screw 1042 helps contain the bone fusion material and alsostrengthens the proximal end wall of the cage body 1010.

In another aspect of the invention, as shown in FIGS. 15-23, theexpandable cage comprises a cage body 1010 having an upper portion 1012and a lower portion 1018. The upper portion and lower portion areconnected and define an internal space 1030.

In this exemplified aspect, the elongate expander is positioned at leastpartially within the internal space such that translation of theelongate expander proximally toward the trailing end expands the cagebody by separating the at least a portion of the upper portion from atleast a portion of the lower portion. In this aspect, the trailing, orproximal end 1078 of the elongate expander 1032 defines an aperture 1040in communication with the internal space 1030.

In one aspect, the trailing, or proximal end 1078 of the elongateexpander is cannulated and has internal threads. The internal threadsare configured to engage the external threads of an actuating screw1200. The actuating screw 1200 engages the elongate expander 1032.Rotation of the actuating screw in a first direction moves the elongateexpander proximally and rotation of the actuating screw in a seconddirection moves the elongate expander distally.

In one aspect, the actuating screw 1200 defines an internal passageway1210 in communication with the internal space 1030, as shown in FIGS.3B, 15, 18, and 19. In this aspect, the internal passageway permitsingress of a bone growth enhancer post expansion of the expandable cage.When positioned within the aperture 1040, the internal passageway 1210of the actuating screw 1200 permits ingress of bone growth enhancer intothe internal space.

Also presented herein is a method for inserting and expanding a cageassembly within an intervertebral space in the spine.

In use, the cage assembly 1000 may be inserted into an intervertebralspace; for example, in the lumbar region of the spine. An expander 1032may be inserted through the proximal opening in the body 1010. Theexpander 1032 may be driven by a tool so that it drives apart the twoportions 1012, 1018 of the body 1010. In one aspect, the body 1010 isselectively expandable because the expander 1032 may be inserted and/orcounter-inserted until the body 1010 achieves the size and shape desiredby the surgeon.

Bone fusion material may be inserted into the one or more windows 1050into the body 1010, and thereby into the proximity of the surroundingbony structures, in order to further secure the cage assembly 1000 inplace. In the aspect having a cannulated actuation screw, the bonefusion material may be inserted post expansion via the internalpassageway of the actuating screw.

In another aspect, a cap 1042 such as the cap screw shown in FIG. 2B maybe inserted into the proximal end of the body 1010. The cap 1042 helpscontain the bone fusion material and also strengthens the proximal endwall of the cage body 1010.

Although several aspects of the invention have been disclosed in theforegoing specification, it is understood by those skilled in the artthat many modifications and other aspects of the invention will come tomind to which the invention pertains, having the benefit of the teachingpresented in the foregoing description and associated drawings. It isthus understood that the invention is not limited to the specificaspects disclosed herein above, and that many modifications and otheraspects are intended to be included within the scope of the appendedclaims. Moreover, although specific terms are employed herein, as wellas in the claims which follow, they are used only in a generic anddescriptive sense, and not for the purposes of limiting the describedinvention, nor the claims which follow.

I claim:
 1. An expandable cage for insertion into an intervertebralspace, comprising: a cage body having a leading end, a trailing end, anupper portion and a lower portion, the upper portion having a an upperbone contact surface and an upper portion lower surface, the lowerportion having a lower bone contact surface and a lower portion uppersurface, wherein the upper portion and lower portion are connected andwherein the upper portion lower surface and lower portion upper surfacedefine an internal space, wherein the trailing end defines an aperturein communication with the internal space; an elongate expanderpositioned at least partially within the internal space, whereintranslation of the elongate expander proximally toward the trailing endexpands the cage body by separating the at least a portion of the upperportion from at least a portion of the lower portion; and an actuatingscrew positioned within the aperture and defining an internal passagewayin communication with the internal space.
 2. The expandable cage ofclaim 1, wherein the upper portion has an upper portion inner surfaceand the lower portion has a lower portion inner surface, and whereinportions of the distal portion of the expander are complimentarilyshaped with at least one of the upper portion inner surface and thelower portion inner surface, whereby pulling the expander proximallycams the distal portion of the expander against the at least one of theupper portion inner surface and the lower portion inner surface toexpand the cage body.
 3. The expandable cage of claim 1, furthercomprising a means to retain the cage body in the unexpanded positionand resist expansion during insertion of the expandable cage into theintervertebral space.
 4. The expandable cage of claim 1, wherein theactuating screw is sized and shaped to complimentarily fit within theaperture, to move the elongate expander in a longitudinal direction, andto retain the expander in the second position.
 5. The expandable cage ofclaim 4, wherein the internal passageway permits ingress of a bonegrowth enhancer post expansion of the expandable cage.
 6. The expandablecage of claim 1, wherein the cage body defines one or more windows incommunication with the internal space.
 7. The expandable cage of claim1, wherein a portion of the upper portion substantially adjacent thetrailing end defines a first trough and a portion of the lower portionsubstantially adjacent the trailing end defines a second trough.
 8. Theexpandable cage of claim 7, further comprising a first shim positionedwithin the first trough and a second shim positioned within the secondtrough, wherein the first and second shims define an orificesubstantially coaxial with the internal passageway.
 9. The expandablecage of claim 8, wherein the actuating screw comprises a head having ahead diameter, and wherein the orifice has an orifice diameter, andwherein the orifice diameter is smaller than the head diameter.
 10. Theexpandable cage of claim 9, wherein, when the elongate expander ispulled proximately the first and second shims are sandwiched between theelongate expander and the head of the actuating screw.
 11. An expandablecage for insertion into an intervertebral space, comprising: a cage bodyhaving a leading end, a trailing end, an upper portion and a lowerportion, the upper portion having a an upper bone contact surface and anupper portion lower surface, the lower portion having a lower bonecontact surface and a lower portion upper surface, wherein the upperportion and lower portion are connected and wherein the upper portionlower surface and lower portion upper surface define an internal space,wherein the trailing end defines an aperture in communication with theinternal space; an elongate expander positioned at least partiallywithin the internal space, wherein translation of the elongate expanderproximally toward the trailing end expands the cage body by separatingthe at least a portion of the upper portion from at least a portion ofthe lower portion, wherein a portion of the upper portion substantiallyadjacent the trailing end defines a first trough and a portion of thelower portion substantially adjacent the trailing end defines a secondtrough; an actuating screw positioned within the aperture and definingan internal passageway in communication with the internal space; and afirst shim positioned within the first trough and a second shimpositioned within the second trough, wherein the first and second shimsdefine an orifice substantially coaxial with the internal passageway.12. The expandable cage of claim 11, wherein the actuating screwcomprises a head having a head diameter, and wherein the orifice has anorifice diameter, and wherein the orifice diameter is smaller than thehead diameter.
 13. The expandable cage of claim 12, wherein, when theelongate expander is pulled proximately the first and second shims aresandwiched between the elongate expander and the head of the actuatingscrew.
 14. The expandable cage of claim 13, wherein an insertion toolmoves the expander from the first position to the second position bypulling the expander proximally.
 15. A system comprising: an expandablecage comprising: a cage body having a leading end, a trailing end, anupper portion and a lower portion, the upper portion having a an upperbone contact surface and an upper portion lower surface, the lowerportion having a lower bone contact surface and a lower portion uppersurface, wherein the upper portion and lower portion are connected andwherein the upper portion lower surface and lower portion upper surfacedefine an internal space, wherein the trailing end defines an aperturein communication with the internal space; an elongate expanderpositioned at least partially within the internal space, whereintranslation of the elongate expander proximally toward the trailing endexpands the cage body by separating the at least a portion of the upperportion from at least a portion of the lower portion; and a actuatingscrew positioned within the aperture and defining an internal passagewayin communication with the internal space; and an insertion tool forinserting the expandable cage between two adjacent vertebrae, theinsertion tool being cannulated and defining an internal chamber. 16.The system of claim 15, wherein the insertion tool comprises an outersleeve defining the internal chamber and a drive rod positioned withinthe internal chamber, and wherein a distal portion of the outer sleeveis configured for releasable engagement with a portion of the trailingend of the expandable cage.
 17. The system of claim 15, wherein a distalend of the drive rod is configured to engage a portion of the actuatingscrew to enable rotation thereof.
 18. The system of claim 16, whereinrotation of the actuating screw in a first direction pulls the elongateexpander proximally, expanding the cage body.
 19. The system of claim15, wherein the internal chamber is in communication with the internalpassageway.